cmd/bent: change to use module-mode for building

also tweaks for performance dashboard
also build tags to turn off broken unsafe code in some benchmarks
also corrected profiling for new run directory

Change-Id: I27f484e52de4ce55f90bb3f122be72127a3181b4
Reviewed-on: https://go-review.googlesource.com/c/benchmarks/+/354410
Trust: David Chase <drchase@google.com>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>
5 files changed